Non-welding type concrete-filled steel tube column having slot and method for fabricating the same

ABSTRACT

A non-welding type concrete-filled steel tube column utilizing a slot, in which an external steel tube is bended and retracted to allow a jointing portion thereof to be formed as a T-shaped bending part is provided. A slot is inserted into the T-shaped bending part in a sliding manner to construct in a non-welding manner, and a multi-perforated penetrating part can be formed on the external steel tube to secure fire resistance capacity thereof. A method of fabricating the same is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2011-0127251, filed on Nov. 30, 2011, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a concrete-filled steel tube column, more particularly, a concrete-filled steel tube column (“CFT”) employing a slot, which can be fabricated in a non-welding manner, and a method for fabricating the same.

BACKGROUND ART

In general, a concrete-filled steel tube column structure is a structure in which an enclosed-type steel tube column is filled with concrete. This structure is structurally stable in terms of stiffness yield strength and transformation and has an excellent advantage with respect to fire resistance and construction and the like. In the above concrete-filled steel tube column structure, in other words, a steel tube formed of a closed section member and withstanding against a bending moment is placed on the outside, and concrete withstanding an axial force is disposed in the inside so that the steel tube restricts the internal concrete or the concrete prevents local buckling of the steel tube from being generated. Due to the above effects, the concrete-filled steel tube column structure is advantageous in that, as compared with another structure, strength and energy absorbing capacity are excellent.

Since the steel tube employed for fabricating the above concrete-filled steel tube column structure should be fabricated through a welding process at a large-scaled factory provided with specific manufacturing facilities, the concrete-filled steel tube column structure has a drawback of excessive manufacturing cost.

In addition, in the above concrete-filled steel tube column structure, if an external force is applied to the steel tube constituting the column, an out-of-plane deformation is easily generated. Accordingly, if the concrete-filled steel tube column structure is designed for applying a rigid joint manner, a suitable reinforcement is considered to provide a joint portion of the column and a beam with sufficient stiffness and yield strength. Various methods are employed as a method for reinforcing a joint portion of the column-beam in the concrete-filled steel tube, and for example, an inner diaphragm method, a penetrating diaphragm method and an outer diaphragm method have been widely utilized.

In the meantime, FIG. 1 is a view illustrating a shape of a test specimen of a conventional concrete-filled steel tube column.

FIG. 1 illustrates that the above concrete-filled steel tube column is fabricated as a test specimen. The concrete-filled steel tube column used as the test specimen 50 is constructed as a structure including an upper cover plate, an end plate, concrete and steel. Concrete is placed and cured on an upper side of the concrete-filled steel tube column specimen. The concrete is then ground and the upper end plate is welded.

FIG. 2 is a view illustrating a verification experiment for comparing and analyzing shrinkage of a concrete-filled steel tube column in fire. In the case of the concrete-filled steel tube column structure, the parameters influencing fire resistance capacity may be drawn as the loading condition, an axial force, a column strength, a sectional size and a boundary condition. The verification experiment is carried out to analyze a degree with respect to the four factors influencing fire resistance capacity.

FIG. 3 is a view for comparing deformation characteristics according to an axial force ratio obtained by the verification experiment of FIG. 2.

FIG. 4 is a view illustrating high-strength concrete placed in the steel tube of the concrete-filled steel tube column. Referring to a change in temperature according to the depth of the concrete corresponding to a spalling state shown in FIG. 4, the high-strength concrete has a drawback of generating spalls caused by vapor in the concrete, and due to the spalling, the steel tube on which a plurality of welding points are exposed has a drawback of extreme vulnerability to fire.

In the meantime, as a conventional art, Korean Patent No. 10-684931 discloses the invention entitled “prefabricated enclosed-type steel skeleton member employing bending-formed steel plate and its installation structure”. The above prior art is illustrated with reference to FIG. 6( a) to FIG. 6( c).

FIG. 6( a) to FIG. 6( c) illustrate a prefabricated enclosed-type steel skeleton member using a bending-formed steel plate according to a conventional art.

Referring to FIG. 6( a) to FIG. 6( c), the prefabricated enclosed-type steel skeleton member using a bending-formed steel plate according to the conventional art is characterized in that a plurality of unit members 10 obtained by bending-forming the steel plate are assembled to complete an enclosed type hollow steel skeleton member having a circular or square tube section. In other words, the steel plate is bending-formed to provide a plurality of unit members 10, each of which include a face-forming part 11 having a shape coinciding with a portion of a section of the tube, and bending portions 12 formed by bending both end portions of the face forming part 11 toward an inner side of the tube. The unit members 10 are disposed such that the bending portions of adjacent unit members contact each other, and the bending portions are then welded to each other to form the hollow steel skeleton member having an enclosed section.

In a unit member 10, at this time, a bending corner at which the face-forming part 11 meets the bending portion 12, is naturally machined to a rounded shape during a bending process, and so once the unit members 10 are disposed such that the bending portions 12 are in contact with each other, a portion at which the bending corners are met is formed into a depression portion 20 which is dented with respect to the face-forming portion 11.

However, the prefabricated enclosed-type steel skeleton member employing bending-formed steel plate according to the prior art has the structure in which four L-shaped unit members are connected and welded. The above steel skeleton member is disadvantageous in that due to melting of a welding agent on the welding portion which is most vulnerable in fire, the welding portion is broken so that the steel tube can burst.

In the meantime, in Korean manufacturing plants for manufacturing concrete-filled steel tube columns, a semi-circular mold is typically utilized for fabricating the concrete-filled steel tube column. In order to remove the concrete from the mold after curing the cement, two semi-circular forms are employed as one circular mold. At this time, the circular steel tube may be employed as a disposable mold rather than a reuse of the mold. However, the main usage purpose of the concrete-filled steel tube column on the market is aimed at preventing water or oil or pressurized gas contained fully therein from leaking therefrom, so careful attention is required to weld the joint portion at the time of fabricating the concrete-filled steel tube column.

As another conventional art, Korean Patent No. 10-991337 discloses the invention entitled “method for manufacturing hollow CFT using rib steel tube”.

FIG. 7 is a sectional view of a centrifugal hollow rib steel tube CFT.

Referring to FIG. 7, in a centrifugal hollow rib steel tube CFT (30) according to the conventional art, like a concrete file, a wire mesh is inserted in a steel tube, and concrete is then placed in the steel tube. Subsequently, the concrete is compressed by means of centrifugal force to form a hollow circular section. At this time, both end portions of each of a pair of semi-cylindrical steel tubes are bent toward a semi-circular shape inside to form a “

” shaped rib. When two semi-cylindrical steel tubes are stood face to face to form a cylindrical steel tube, a pair of small C-section steels is fitted to allow each C-section steel to tie one pair of ribs so that two semi-cylindrical steel tubes are constructed to one cylindrical steel tube.

In the centrifugal hollow rib steel tube CFT according to the conventional art, however, the method for coupling only the steel tubes itself has problems of low coupling force and small coupling depth in the concrete. In addition, restriction obtained by only the C-section steel can cause a burst of the concrete-filled steel tube due to a concentration of internal pressure in the concrete to an external steel tube in fire.

The following patent documents are conventional art.

Patent document 1: Korean Patent No. 10-684931 (Filing date: Feb. 28, 2006) entitled “Prefabricated enclosed-type steel skeleton member employing bending-formed steel plate and its installation structure”;

Patent document 2: Korean Patent No. 10-991337 (Filing date: Sep. 29, 2008), entitled “Method for manufacturing hollow CFT using rib steel tube”;

Patent document 3: Korean Patent No. 10-1062928 (Filing date: May 27, 2009), entitled “Concrete-filled steel tube”;

Patent document 4: Korean Patent Laid-open Publication No. 2010-76576 (Publication date: Jul. 6, 2010), entitled “Concrete-filled steel tube having improved lateral confinement force”;

Patent document 5: Korean Patent No. 10-766661 (Filing date: May 25, 2006), entitled “Concrete-filled steel tube girder”;

Patent document 6: Korean Patent No. 10-763029 (Filing date: Dec. 7, 2006), entitled “Concrete-filled steel tube beam”.

SUMMARY

To solve the above problems, the technical solution achieved by the present invention is to provide a non-welding type concrete-filled steel tube column utilizing a slot, in which an external steel tube is bended and retracted to allow a jointing portion thereof to be formed as a T-shaped bending part, and a slot is inserted into the T-shaped bending part in a sliding manner to construct in a non-welding manner, and a method of fabricating the same.

Another technical solution achieved by the present invention is to provide a non-welding type concrete-filled steel tube column utilizing a slot, in which a multi-perforated penetrating part can be formed on the external steel tube to secure fire resistance capacity thereof, and a method of fabricating the same.

As the means for achieving the above technical objects, the non-welding type concrete-filled steel tube column utilizing a slot according to the present invention comprises an external steel tube formed of an integrated steel plate and is bended and retracted to allow a jointing portion of both end faces thereof to be formed as a T-shaped bending part, the external steel tube having a multi-perforated penetrating part formed thereon; a slot having a shape corresponding to the shape of the T-shaped bending part to allow the T-shaped bending part to be inserted thereinto; and concrete placed and cured in the external steel tube in a state where the T-shaped bending part is inserted into the slot. Herein, the external steel tube is jointed by the slot in a non-welding manner.

Herein, the slot may have a ‘

’ shape corresponding to the T-shaped bending part, and the ‘

’ shaped slot may be slid along and coupled to the T-shaped bending part to allow the external steel tube to be integrated in a non-welding manner.

The non-welding type concrete-filled steel tube column utilizing a slot according to the present invention may further comprise a ‘

’′-shaped restricting steel fitting coupled to a remaining end portion of the T-shaped bending part, which is not inserted into the ‘

’-shaped slot.

Herein, the multi-perforated penetrating part of the external steel tube is formed on the external steel tube to discharge steam pressure generated in the concrete in fire.

As the means for achieving the above technical objects, the method for fabricating the non-welding type concrete-filled steel tube column utilizing a slot according to the present invention comprises the steps of a) forming a multi-perforated penetrating part on an integrated external steel tube; b) bending and retracting the external steel tube to allow a jointing portion of both end faces of the external steel tube to be formed as a T-shaped bending part; c) fabricating the slot having a shape corresponding to the shape of the T-shaped bending part; d) inserting the T-shaped bending part into the slot to allow the external steel tube to be joined by the slot in the non-welding process; and e) placing and curing concrete in the external steel tube in a state where the T-shaped bending part is inserted into the slot.

Herein, the slot in step c) may have a ‘

’ shape corresponding to the T-shaped bending part.

Herein, the ‘

’ shaped slot may be slid along and coupled to the T-shaped bending part to allow the external steel tube to be integrated in a non-welding manner.

The method for fabricating the non-welding type concrete-filled steel tube column utilizing a slot according to the present invention may further comprise the step of fabricating a ‘

’′-shaped restricting steel fitting and coupling the ‘

’′-shaped restricting steel fitting to a remaining end portion of the T-shaped bending part, which is not inserted into the ‘

’-shaped slot.

Herein, the multi-perforated penetrating part of the external steel tube in step a) discharges steam pressure generated in the concrete in fire.

According to the present invention, the external steel tube of the concrete-filled steel tube column is formed of an integrated steel plate, and is bended and retracted to allow a jointing portion thereof to be formed as the T-shaped bending part, and the slot is inserted into the T-shaped bending part in a sliding manner so that construction can be performed without welding. Accordingly, since a welding process is omitted, the time required for constructing the concrete-filled steel tube column can be reduced.

According to the present invention, the multi-perforated penetrating part can be formed on the external steel tube of the concrete-filled steel tube column to secure fire resistance capacity of the concrete-filled steel tube column. Accordingly, it is possible to remove steam pressure in the concrete.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating the shape of a test specimen of a conventional concrete-filled steel tube column;

FIG. 2 is a view illustrating a verification experiment for comparing and analyzing shrinkage of a concrete-filled steel tube column in fire;

FIG. 3 is a view for comparing deformation characteristics according to an axial force ratio obtained by the verification experiment of FIG. 2;

FIG. 4 is a view for illustrating a spalling state caused by steam in concrete;

FIG. 5 is a view showing a change in temperature according to the depth of concrete corresponding to the spalling state of FIG. 4;

FIG. 6( a) to FIG. 6( c) illustrate a prefabricated enclosed-type steel skeleton member using a bending-formed steel plate according to a conventional art;

FIG. 7 is a sectional view of a centrifugal hollow rib steel tube CFT;

FIG. 8( a) and FIG. 8( b) illustrate an example of a non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention;

FIG. 9( a) and FIG. 9( b) illustrate an example of a concrete-filled steel tube column prior to utilizing a slot in a method for fabricating a non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention;

FIG. 10 is a view showing that, in a method for fabricating a non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, a concrete-filled steel tube column is fabricated by employing a slot in a non-welding manner; and

FIG. 11 is a view illustrating a bending part of an external steel tube fabricated by a slot in a non-welding manner.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

Hereinafter, the preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings for enabling a one skilled in the art to embody easily the present invention. However, the present invention is not limited to the embodiments described above herein, but can be embodied variously. In order to illustrate clearly the present invention, in addition, parts which are not relevant to the present invention are omitted in the drawings, and similar parts are indicated by similar reference numerals throughout the entire description.

Unless otherwise indicated, in the entire specification, the sentence of “some portion includes some structural elements” means that another structural element is not excluded, but may be further included.

FIG. 8( a) and FIG. 8( b) illustrate an example of a non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, a) in FIG. 8 is a perspective view and b) in FIG. 8 is a plane view.

Referring to FIG. 8( a) and FIG. 8( b), a non-welding type concrete-filled steel tube column 100 utilizing a slot according to an embodiment of the present invention includes an external steel tube 110, a multi-perforated penetrating part 120, a bending part 130, a slot 140, a restricting steel fitting 150 and concrete 160.

The external steel tube 110 is formed of an integrated steel plate, and is bended and retracted to allow a jointing portion of both end faces thereof to be formed as the T-shaped bending part 130. At this time, the multi-perforated penetrating part 120 is formed on the external steel tube 110, and so steam pressure generated in the concrete 160 in fire can be discharged through the multi-perforated penetrating part 120. In other words, the non-welding type concrete-filled steel tube column 100 utilizing a slot according to an embodiment of the present invention is the CFT structure in which pressure in the internal concrete can be discharged, it is possible to secure fire resistance capacity of the non-welding type concrete-filled steel tube column by efficiently removing steam pressure in the concrete.

More specifically, the external steel tube 110 is a square-shaped steel tube and has an outer width of 20 cm or more. At this time, the external steel tube 110 may have at least one multi-perforated penetrating part 120, which is a steam discharging hole, formed on each of an upper portion and a lower portion thereof for preventing the pressure from increasing in fire. Furthermore, steel material having the yield strength of 240 MPa or more is employed for fabricating the external steel tube 110. Of course, diameter and the number of the multi-perforated penetrating part 120 are adjusted to prevent the concrete from leaking through the multi-perforated penetrating part 120.

The slot 140 is formed such that the slot corresponds to the shape of the T-shaped bending part 130 so as to allow the T-shaped bending part 130 to be inserted into the slot 140. By inserting the T-shaped bending part 130 into the slot 140 as above, both end surfaces of the external steel tube are joined in a non-welding manner by the slot. As shown indicated by reference numeral “A” more concretely, the slot 140 may have the ‘

’ shape corresponding to the shape of the T-shaped bending part 130, and the ‘

’-shaped slot 140 is coupled along the T-shaped bending part 130 in a sliding manner to enable the external steel tube 110 to be integrated in a non-welding manner. In fire, for example, local buckling can occur rapidly on the external steel tube 110 of the concrete-filled steel tube column. In the non-welding type concrete-filled steel tube column 100 utilizing a slot according to an embodiment of the present invention, however, due to stress distribution on the multi-perforated penetrating part 120, it is possible to induce a slow transformation of the concrete-filled steel tube column (CFT).

The ‘

’″-shaped restricting steel fitting 150 is coupled to a remaining end portion of the T-shaped bending part 130, which is not inserted into the ‘

’-shaped slot 140.

In a state where the T-shaped bending part 130 is not inserted into the slot 140, the external steel tube 110 is filled with concrete 160 and the concrete is then cured. More specifically, an ordinary aggregate defined in the general concrete specification is employed for the concrete 160 with which the external steel tube 110 is filled. For example, the specified design strength of the concrete 160 is within the range of 240 kgf/cm² to 400 kgf/cm². Provided that the trusted organization provides the evaluation results of fire resistance capacity for the concrete having the specified design strength of 400 kgf/cm² or more, this concrete may be applied to the present invention.

In the non-welding type concrete-filled steel tube column 100 utilizing a slot according to an embodiment of the present invention, in addition, although the drawing illustrates the square shaped external steel tube 110, the present invention is not limited thereto. For example, a cylindrical shape steel tube may be employed as the external steel tube 110. Also, even though the drawing shows that the bending part 130 has the T-shape, the present invention is not limited thereto. Furthermore, although the drawing shows that the slot 140 corresponding to the T-shaped bending part 130 has the ‘

’-shape, the present invention is not limited thereto. For example, the slot 140 may have a shape obtained by combining the ‘

’-shape slot 140 and the ‘

’′-shaped restricting steel fitting 150.

According to the non-welding type concrete-filled steel tube column 100 utilizing a slot according to an embodiment of the present invention, inner jointing portions of the CFT external steel tube 110 to be filled with concrete 160 is formed as the T-shaped bending part 130 so that a coupling effect of the concrete 160 and the outer steel tube 110 can be increased, and due to the above coupling effect, the problem of lowering the yield strength of the external steel tube 110 exposed to an outside, in fire can be solved through concrete 160 having relatively high fire resistance capacity.

Hereinafter, a method for fabricating the non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention is illustrated with reference to FIG. 9 to FIG. 11.

In the method for fabricating the non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, the multi-perforated penetrating part is firstly formed on the external steel tube which is the integrated steel plate.

FIG. 9( a) and FIG. 9( b) illustrate an example of the concrete-filled steel tube column prior to utilizing a slot in a method for fabricating the non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, a) in FIG. 9 is a perspective view and b) in FIG. 9 is a plane view.

In the non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, since the multi-perforated penetrating part 120 is formed on the external steel tube 110, the pressure of steam in the concrete 160, which is generated in fire as described above, can be discharged through the multi-perforated penetrating part 120. For example, a fire resistance capacity of approximately 100 minutes is shown under an ordinary load condition (load ratio: 0.6) so that the internal pressure of the concrete can be discharged effectively to the outside to increase fire resistance capacity.

In the meantime, FIG. 10 is a view showing that, in the method for fabricating the non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, the concrete-filled steel tube column is fabricated by means of the slot in a non-welding manner, and FIG. 11 is a view illustrating that a bending part of the external steel tube is integrated by the slot in a non-welding manner.

As shown in FIG. 10, an external steel tube 110 is bended and retracted to allow a jointing portion of both end faces thereof to be formed as the T-shaped bending part 130, and the slot 140 corresponding to the shape T-shaped bending part 130 is subsequently formed. Then, the T-shaped bending part 130 of the external steel tube is inserted into the slot so as to allow the external steel tube 110 to be joined by the slot 140 in a non-welding manner. At this time, the slot 140 has the ‘

’ shape so as to correspond to the T-shaped bending part 130, the ‘

’-shaped slot 140 is slid along and coupled to the T-shaped bending part 130 to enable the external steel tube 110 to be integrated in a non-welding manner Then, the ‘

’′-shaped restricting steel fitting is fabricated, and the ‘

’′-shaped restricting steel fitting is coupled to the remaining end portion of the T-shaped bending part, which is not inserted into the ‘

’-shaped slot 140.

In the non-welding type concrete-filled steel tube column utilizing a slot according to an embodiment of the present invention, as shown in FIG. 10, the concrete-filled steel tube column is integrated by means of the “

”-shaped slot 140 in a non-welding manner. In other words, since the T-shaped bending part 130 is inserted along the “

”-shaped slot 140, the T-shaped bending part can be coupled to the slot without welding. As shown in FIG. 11, to put it concretely, the “

”-shaped slot 140 is slid in the longitudinal direction of the T-shaped bending part 130 and coupled to the T-shaped bending part. At this time, the “

”-shaped slot 140 corresponding to the T-shaped bending part 130 is fabricated in advance and then provided.

Furthermore, the ‘

’′-shaped restricting steel fitting may be coupled to the remained portion of the T-shaped bending part 130, which is not inserted into the ‘

’-shapedslot 140.

In sequence, in a state where the T-shaped bending part 130 is inserted into the slot 140, concrete is placed in the external steel tube 110 and then cured so that the non-welding type concrete-filled steel tube column utilizing a slot is fabricated.

Ultimately, according to the non-welding type concrete-filled steel tube column utilizing a slot and the method for fabricating the same according to the embodiment of the present invention, the CFT external steel tube is formed of a conventional integrated steel plate and is bended and retracted to allow a jointing portion thereof to be formed as the T-shaped bending part 130, and T-shaped bending part is then inserted into the slot in a sliding manner, whereby the concrete-filled steel tube column is constructed by the non-welding manner. Accordingly, a welding process can be omitted to reduce the construction time of the concrete-filled steel tube column. In addition, the multi-perforated penetrating part is formed on the external steel tube of the concrete-filled steel tube column so that fire resistance capacity of the concrete-filled steel tube column can be secured. Due to the above, steam pressure in the concrete can be removed effectively.

The embodiment described herein is generally described as one example of the present invention, one skilled in the art to which the disclosure pertains may understand that the present invention can be easily changed into another specific embodiment without a modification of the scope and essential features of the present invention. Accordingly, it is to be understood that the disclosure is only one example in all the aspects and is not to be limited to the embodiment. For example, the structural elements illustrated as the combined element may be individually utilized, and the structural elements illustrated as the separated element may be combined and employed.

The above description should not be taken as limiting the scope of the present invention which is defined by the appended claims and it should be understood that all the modifications and alternative constructions derived from the meaning and scope of the claims and their equivalents is included in the scope of the present invention. 

What is claimed is:
 1. A concrete-filled steel tube column (CFT), comprising; an external steel tube formed of an integrated steel plate and is bended and retracted to allow a jointing portion of both end faces thereof to be formed as a T-shaped bending part, the external steel tube having a multi-perforated penetrating part formed thereon; a slot having a shape corresponding to the shape of the T-shaped bending part to allow the T-shaped bending part to be inserted thereinto; and concrete placed and cured in the external steel tube in a state where the T-shaped bending part is inserted into the slot; wherein the external steel tube is jointed by the slot in a non-welding manner.
 2. The non-welding type concrete-filled steel tube column utilizing a slot of claim 1, wherein the slot has a ‘

’ shape corresponding to the T-shaped bending part.
 3. The non-welding type concrete-filled steel tube column utilizing a slot of claim 2, wherein the ‘

’ shaped slot is slid along and coupled to the T-shaped bending part to allow the external steel tube to be integrated in a non-welding manner.
 4. The non-welding type concrete-filled steel tube column utilizing a slot of claim 3, further comprising a ‘

’′-shaped restricting steel fitting coupled to a remaining end portion of the T-shaped bending part, which is not inserted into the ‘

’-shaped slot.
 5. The non-welding type concrete-filled steel tube column utilizing a slot of claim 1, wherein the multi-perforated penetrating part of the external steel tube discharges steam pressure generated in the concrete in fire.
 6. A method of fabricating a concrete-filled steel tube column (CFT), comprising the steps of; a) forming a multi-perforated penetrating part on an integrated external steel tube; b) bending and retracting the external steel tube to allow a jointing portion of both end faces of the external steel tube to be formed as a T-shaped bending part; c) fabricating a slot having a shape corresponding to the shape of the T-shaped bending part; d) inserting the T-shaped bending part into the slot to allow the external steel tube to be joined by the slot in a non-welding process; and e) placing and curing concrete in the external steel tube in a state where the T-shaped bending part is inserted into the slot.
 7. The method of fabricating the non-welding type concrete-filled steel tube column utilizing a slot of claim 6, wherein the slot in step c) has a ‘

’ shape corresponding to the T-shaped bending part.
 8. The method of fabricating the non-welding type concrete-filled steel tube column utilizing a slot of claim 7, wherein the ‘

’ shaped slot is slid along and coupled to the T-shaped bending part to allow the external steel tube to be integrated in a non-welding manner.
 9. The method of fabricating the non-welding type concrete-filled steel tube column utilizing a slot of claim 8, further comprising the step of fabricating a ‘

’′-shaped restricting steel fitting, and coupling the ‘

’′-shaped restricting steel fitting to a remaining end portion of the T-shaped bending part, which is not inserted into the ‘

’-shaped slot, between step d) and step e).
 10. The method of fabricating the non-welding type concrete-filled steel tube column utilizing a slot of claim 6, wherein the multi-perforated penetrating part of the external steel tube in step a) discharges steam pressure generated in the concrete in fire. 